This invention relates in general to wind turbine platforms. In particular, this invention relates to an improved method of assembling a floating wind turbine platform and an improved method for mooring such a floating wind turbine platform.
Wind turbines for converting wind energy to electrical power are known and provide an alternative energy source for power companies. On land, large groups of wind turbines, often numbering in the hundreds of wind turbines, may be placed together in one geographic area. These large groups of wind turbines can generate undesirably high levels of noise and may be viewed as aesthetically unpleasing. An optimum flow of air may not be available to these land-base wind turbines due to obstacles such as hills, woods, and buildings.
Groups of wind turbines may also be located offshore, but near the coast at locations where water depths allow the wind turbines to be fixedly attached to a foundation on the seabed. Over the ocean, the flow of air to the wind turbines is not likely to be disturbed by the presence of various obstacles (i.e., as hills, woods, and buildings) resulting in higher mean wind speeds and more power. The foundations required to attach wind turbines to the seabed at these near-coast locations is relatively expensive, and can only be accomplished at relatively shallow depths, such as a depth of up to about 25 meters.
The U.S. National Renewable Energy Laboratory has determined that winds off the U.S. Coastline over water having depths of 30 meters or greater have an energy capacity of about 3,200 TWh/yr. This is equivalent to about 90 percent of the total U.S. energy use of about 3,500 TWh/yr. The majority of the offshore wind resource resides between 37 and 93 kilometers offshore where the water is over 60 meters deep. Fixed foundations for wind turbines in such deep water are not likely economically feasible. This limitation has led to the development of floating platforms for wind turbines.
Known floating wind turbine platforms are formed from steel and are based on technology developed by the offshore oil and gas industry. Other examples of floating wind turbine platform are described in PCT Application No. PCT/US2011/059335, filed Nov. 4, 2011 (published as PCT Publication No. WO2012061710 A2 on May 10, 2012), U.S. patent application Ser. No. 13/863,074, filed Apr. 15, 2013 (published as U.S. Patent Application Publication No. 2013/0233231 A1 on Sep. 12, 2013), and PCT Application No. PCT/US2014/057236, filed Sep. 24, 2014 (published as PCT Publication No. WO2012061710 A2 on May 10, 2012), the disclosures of which are incorporated herein by reference. There remains however, a need to provide improved methods of assembling and mooring a floating wind turbine platform.